Ribonuclease P (RNase P) is the essential ribonucleoprotein (RNP) enzyme responsible for generating mature tRNAs prior to protein synthesis, and also interacts with various other RNAs (including viral and phage RNA, mRNA, non-coding RNA, rRNA, and riboswitches). In eukaryotes, RNase P components additionally function as coordinators of mRNA in processing bodies, and regulate transcription by binding to the chromatin of non-coding RNA genes. As biological functions of RNase P emerge, it is critical to understand the structural basis of RNA recognition and catalysis by RNase P. The objective of the proposed research is to define the RNase P complex with bound precursor tRNA and to understand the mechanism of RNA/RNA recognition at atomic resolution. Individual structures of P RNAs, several tRNAs, and various RNase P proteins are known, but it is unclear how these components fit together within a macromolecular context. I hypothesize that high sequence conservation present within specific P RNA regions is a reflection of strong structural constraints, affecting RNA folding, substrate recognition, and catalysis. The aims of this project are: 1) to define the three-dimensional structure of a ~150 kDa ternary complex of holoenzyme RNase P with bound precursor tRNA substrate, and 2) to ascertain how universally conserved RNase P regions participate in RNA recognition and catalysis. Crystallography, biophysical methods, and molecular biology techniques will be utilized to characterize the structure and recognition elements of the RNase P/tRNA complex. To obtain atomic level diffraction, optimization screening and RNA recombinant strategies will be implemented. Heavy metal derivatization will be used not only in structure determination, but also to identify metal ions within the active site. PUBLIC HEALTH RELEVANCE: Work detailed in this proposal will provide important clues on how structured RNA molecules recognize each other, and has relevant implications for human diseases attributed to RNA processing. Alteration of RNase P specificity has been shown to efficiently degrade disease causing mRNAs for the treatment of leukemia (chronic myelogenous leukemia) and viruses, such as such as herpes simplex virus and cytomegalovirus. In addition, RNA-mediated catalysis by RNase P at the molecular level will give insight into RNA processing mechanisms associated with cancers (>15) and neurodegenerative diseases. Lastly, defining the RNase P- tRNA interface will provide important structural information that will greatly assist the development of RNA targeted chemotherapeutic drug strategies.